I can't add cuts to a plane
Pick a direction

The operation you are trying to perform is called "Loop cuts and slide": basically recognize on the mesh faces a certain flow of polygons (loop) and allow the user to subdivide the interested faces by adding a given amount of edges.

What the command need to run is just the direction of the path. Quad faces can in fact be subdivided in two different directions.

Till the cursor does't approach one of the edges, you'll not see the pink edges (the future loop cuts).